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Commit9426047

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Clean up bogosities in use of random(3) and srandom(3) --- do not assume
that RAND_MAX applies to them, since it doesn't. Instead add aconfig.h parameter MAX_RANDOM_VALUE. This is currently set at 2^31-1but could be auto-configured if that ever proves necessary. Also fixsome outright bugs like calling srand() where srandom() is appropriate.
1 parent259489b commit9426047

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8 files changed

+47
-25
lines changed

8 files changed

+47
-25
lines changed

‎doc/src/sgml/func.sgml

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Original file line numberDiff line numberDiff line change
@@ -171,6 +171,18 @@
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<entry>convert floating point to integer</entry>
172172
<entry>integer(2.0)</entry>
173173
</row>
174+
<row>
175+
<entry>random()</entry>
176+
<entry>float8</entry>
177+
<entry>random value in the range 0.0 to 1.0</entry>
178+
<entry>random()</entry>
179+
</row>
180+
<row>
181+
<entry>setseed(float8)</entry>
182+
<entry>int</entry>
183+
<entry>set seed for subsequent random() calls</entry>
184+
<entry>setseed(0.54823)</entry>
185+
</row>
174186
</tbody>
175187
</tgroup>
176188
</table>

‎doc/src/sgml/ref/set.sgml

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/ref/set.sgml,v 1.46 2000/07/14 15:27:14 thomas Exp $
2+
$Header: /cvsroot/pgsql/doc/src/sgml/ref/set.sgml,v 1.47 2000/08/07 00:51:18 tgl Exp $
33
Postgres documentation
44
-->
55

@@ -194,9 +194,9 @@ SET TIME ZONE { '<replaceable class="PARAMETER">timezone</replaceable>' | LOCAL
194194
<listitem>
195195
<para>
196196
The value for the seed to be used by the
197-
<function>random</function>catalogfunction.Significant
197+
<function>random</function> function.Allowed
198198
values are floating point numbers between 0 and 1, which
199-
are then multiplied byRAND_MAX. This product will
199+
are then multiplied by2^31-1. This product will
200200
silently overflow if a number outside the range is used.
201201
</para>
202202

‎src/backend/optimizer/geqo/geqo_main.c

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $Id: geqo_main.c,v 1.22 2000/06/28 03:31:45 tgl Exp $
10+
* $Id: geqo_main.c,v 1.23 2000/08/07 00:51:23 tgl Exp $
1111
*
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*-------------------------------------------------------------------------
1313
*/
@@ -106,9 +106,9 @@ geqo(Query *root)
106106
/* seed random number generator */
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/* XXX why is this done every time around? */
108108
if (Geqo_random_seed >=0)
109-
srandom(Geqo_random_seed);
109+
srandom((unsignedint)Geqo_random_seed);
110110
else
111-
srandom(time(NULL));
111+
srandom((unsignedint)time(NULL));
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113113
/* allocate genetic pool memory */
114114
pool=alloc_pool(pool_size,number_of_rels);

‎src/backend/postmaster/postmaster.c

Lines changed: 2 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,7 @@
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*
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*
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* IDENTIFICATION
14-
* $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.158 2000/07/28 02:13:26 tgl Exp $
14+
* $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.159 2000/08/07 00:51:30 tgl Exp $
1515
*
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* NOTES
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*
@@ -1850,7 +1850,7 @@ DoBackend(Port *port)
18501850
*/
18511851
random_seed=0;
18521852
gettimeofday(&now,&tz);
1853-
srandom(now.tv_usec);
1853+
srandom((unsignedint)now.tv_usec);
18541854

18551855
/* ----------------
18561856
* Now, build the argv vector that will be given to PostgresMain.
@@ -2029,7 +2029,6 @@ RandomSalt(char *salt)
20292029
staticlong
20302030
PostmasterRandom(void)
20312031
{
2032-
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staticboolinitialized= false;
20342033

20352034
if (!initialized)

‎src/backend/utils/adt/float.c

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Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
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*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/utils/adt/float.c,v 1.67 2000/08/01 18:29:35 tgl Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/utils/adt/float.c,v 1.68 2000/08/07 00:51:14 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -1315,7 +1315,7 @@ drandom(PG_FUNCTION_ARGS)
13151315
float8result;
13161316

13171317
/* result 0.0-1.0 */
1318-
result= ((double)random()) /RAND_MAX;
1318+
result= ((double)random()) /((double)MAX_RANDOM_VALUE);
13191319

13201320
PG_RETURN_FLOAT8(result);
13211321
}
@@ -1328,7 +1328,7 @@ Datum
13281328
setseed(PG_FUNCTION_ARGS)
13291329
{
13301330
float8seed=PG_GETARG_FLOAT8(0);
1331-
intiseed= (seed*RAND_MAX);
1331+
intiseed= (int) (seed*MAX_RANDOM_VALUE);
13321332

13331333
srandom((unsignedint)iseed);
13341334

‎src/backend/utils/adt/misc.c

Lines changed: 8 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
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*
99
*
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* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/utils/adt/misc.c,v 1.19 2000/06/05 07:28:52 tgl Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/utils/adt/misc.c,v 1.20 2000/08/07 00:51:14 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -45,23 +45,25 @@ nonnullvalue(PG_FUNCTION_ARGS)
4545

4646
/*
4747
* oidrand (oid o, int4 X)-
48-
*takes in an oid and a int4 X, and will return 'true'
49-
*about 1/X ofthe time.
48+
*Takes in an oid and a int4 X, and will return 'true' about 1/X of
49+
*the time. If X == 0, this will always return true.
5050
* Useful for doing random sampling or subsetting.
51-
*if X == 0, this will always return true;
5251
*
5352
* Example use:
5453
* select * from TEMP where oidrand(TEMP.oid, 10)
5554
* will return about 1/10 of the tuples in TEMP
5655
*
56+
* NOTE: the OID input is not used at all. It is there just because of
57+
* an old optimizer bug: a qual expression containing no variables was
58+
* mistakenly assumed to be a constant. Pretending to access the row's OID
59+
* prevented the optimizer from treating the oidrand() result as constant.
5760
*/
5861

5962
staticboolrandom_initialized= false;
6063

6164
Datum
6265
oidrand(PG_FUNCTION_ARGS)
6366
{
64-
/* XXX seems like we ought to be using the oid for something? */
6567
#ifdefNOT_USED
6668
Oido=PG_GETARG_OID(0);
6769
#endif
@@ -96,7 +98,7 @@ oidsrand(PG_FUNCTION_ARGS)
9698
{
9799
int32X=PG_GETARG_INT32(0);
98100

99-
srand(X);
101+
srandom((unsignedint)X);
100102
random_initialized= true;
101103
PG_RETURN_BOOL(true);
102104
}

‎src/include/config.h.in

Lines changed: 10 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
* or in config.h afterwards. Of course, if you edit config.h, then your
99
* changes will be overwritten the next time you run configure.
1010
*
11-
* $Id: config.h.in,v 1.128 2000/07/28 02:13:40 tgl Exp $
11+
* $Id: config.h.in,v 1.129 2000/08/07 00:51:38 tgl Exp $
1212
*/
1313

1414
#ifndefCONFIG_H
@@ -484,6 +484,15 @@ extern long random(void);
484484
externvoidsrandom(unsignedintseed);
485485
#endif
486486

487+
/* The random() function is expected to yield values 0 .. MAX_RANDOM_VALUE */
488+
/* Currently, all known implementations yield 0..2^31-1, so we just hardwire
489+
* this constant. We could do a configure test if it proves to be necessary.
490+
* CAUTION: Think not to replace this with RAND_MAX. RAND_MAX defines the
491+
* maximum value of the older rand() function, which is often different from
492+
* --- and considerably inferior to --- random().
493+
*/
494+
#defineMAX_RANDOM_VALUE (0x7FFFFFFF)
495+
487496
/* Set to 1 if you have libz.a */
488497
#undef HAVE_LIBZ
489498

‎src/include/optimizer/geqo_random.h

Lines changed: 6 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -6,7 +6,7 @@
66
* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
77
* Portions Copyright (c) 1994, Regents of the University of California
88
*
9-
* $Id: geqo_random.h,v 1.6 2000/01/26 05:58:20 momjian Exp $
9+
* $Id: geqo_random.h,v 1.7 2000/08/07 00:51:42 tgl Exp $
1010
*
1111
*-------------------------------------------------------------------------
1212
*/
@@ -26,13 +26,13 @@
2626

2727
#include<math.h>
2828

29-
#defineGEQOMASK 2147483647
29+
/* geqo_rand returns a random float value between 0 and 1 inclusive */
3030

31-
#definegeqo_rand() ((double)random()/GEQOMASK)
31+
#definegeqo_rand() (((double)random()) / ((double) MAX_RANDOM_VALUE))
3232

33-
/* geqo_randint returns integer value
34-
between lower and upper inclusive */
33+
/* geqo_randint returns integer value between lower and upper inclusive */
3534

36-
#definegeqo_randint(upper,lower) ( (int) floor( geqo_rand()*((upper-lower)+0.999999) ) +lower )
35+
#definegeqo_randint(upper,lower) \
36+
( (int) floor( geqo_rand()*(((upper)-(lower))+0.999999) ) + (lower) )
3737

3838
#endif/* GEQO_RANDOM_H */

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